The present invention relates to improvement in frictional agitation joining method and apparatus therefor which are suitable for joining light alloys such as aluminum, aluminum alloy or the like, and in particular to a frictional agitation joining method capable of joining two sheets of members to be joined in a form of substantially an edge joint, and a method therefor.
As shown in FIGS. 1 and 2, a frictional agitation joining method is conducted such that a circular rod-shaped agitation rod 102 having a projecting portion 101 at its distal end is caused to advance in between members W to be joined such as an aluminum alloy in a pressurizing manner while being rotated to generate frictional heat and the heat is conducted to the members W to be joined while the agitation rod is being fed along a joining line 103 so that the members W are joined.
In the joining, the members W to be joined is softened at a temperature of about 70% of their melting points and the softened portions are plastically fluidized according to rotating and feeding of the agitation rod 102 so that joining of the members W is completed as they are in a solid phase state. Incidentally, as the agitation rod 102, a rod made from a tool steel, a stainless steel can be used, and the length of the projecting portion 101, namely a length to be invaded between the members W to be joined, is about the thickness of butting portions of the members W to be joined.
Shoulder faces 104 corresponding to shoulder portions of the projecting portions 101 prevents portions of the members W to be joined from being pressed outside when the projecting portion 101 advances in between the members W to be joined, and they serve to apply frictional heat from the surfaces of the members W to be joined. The members W to be joined which serve as a butting joint are placed on a backing metal 105, or a holding mechanism for supporting the members 4 from their back sides is provided at a position corresponding to that of the backing metal, so that an axial pressurizing force of the agitation rod 102 can be sustained by the backing metal or the holding mechanism.
In such a frictional agitation joining method, there are advantages that (1) there is hardly joined strain, (2) a joined attitude is not limited to specific ones, (3) a high speed joining can be achieved due to a high energy efficiency, (4) there are not any defects such as a bubbles, cracks or the like in a joined joint portion, (5) parameters for joining to be controlled are only the number of rotations and the pressurizing force of the agitation rod, (6) even a material such as DURALUMIN or the like which is considered to be difficult to melt-weld can be joined, and so on.
Incidentally, such a frictional agitation joining technique has been described in Japanese Patent Application Laid-Open (JP-A) No. 2000-33484 publication, JP-A 2000-167676 and the like.
In the above related frictional agitation joining technique, however, the backing metal 105 of the members W to be joined for sustaining the axial pressurizing force of the agitation rod 102 and a controlling/holding mechanism for rotating and feeding the agitation rod 102 in conformal with the joining line 103 are required, so that the conventional frictional agitation joining technique can not be employed for joining a member for a joint structure curved in a 3-dimensional manner, more specifically, a member of sandwiched structure such as a suspension member of an automobile.
Also, since a butting joint form is employed for a joint structure in many cases, it is necessary to control a clearance xe2x80x9caxe2x80x9d and unevenness xe2x80x9cbxe2x80x9d of a joint, as shown in FIG. 3, and the degree of freedom for design is made small. Furthermore, when members W, W to be joined to each other, whose plate thicknesses are different from each other are joined to each other, a difference thickness adjusting margin xe2x80x9ccxe2x80x9d achieved by the backing metal 106 is required, as shown in FIG. 4, which results in increase in cost.
The present invention has been made in view of the above problems, and an object thereof is to provide a frictional agitation joining method which allows joining mainly by not a butting joint form but a so-called edge joint form to be applied to a 3-dimensionally curved joint structure and a method therefor.
In order to achieve the above object, the present invention is configured such that two plate-shaped members to be joined are superimposed one on another such that end faces thereof constitutes generally an edge joint form, and joining is performed by applying frictional agitation energy to the end faces of both the members and inside faces of the members which are positioned near the end faces and are superimposed one on another.
An aluminum member, an aluminum alloy member or another light alloy material similar thereto is representative of the member to be joined. The shape of the member to be joined includes any approximate edge joint form whose joining portion may be curved in a 2-dimensional or 3-dimentional manner is constituted.